PrimeFinder (Nuiton Matrix :: API 2.7 API)

java.lang.Object
- cern.colt.map.PrimeFinder

```
public class PrimeFinder
extends Object
```
Not of interest for users; only for implementors of hashtables. Used to keep hash table capacities prime numbers.
Choosing prime numbers as hash table capacities is a good idea to keep them working fast, particularly under hash table expansions.
However, JDK 1.2, JGL 3.1 and many other toolkits do nothing to keep capacities prime. This class provides efficient means to choose prime capacities.
Choosing a prime is O(log 300) (binary search in a list of 300 int's). Memory requirements: 1 KB static memory.

Version:

1.0, 09/24/99

Author:

wolfgang.hoschek@cern.ch

Field Summary

Fields
Modifier and Type Field Description

static int largestPrime
The largest prime this class can generate; currently equal to Integer.MAX_VALUE.

Constructor Summary

Constructors
Modifier Constructor Description

protected PrimeFinder()
Makes this class non instantiable, but still let's others inherit from it.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`protected static void`	`main(String[] args)`	Tests correctness.
`static int`	`nextPrime(int desiredCapacity)`	Returns a prime number which is `>= desiredCapacity` and very close to `desiredCapacity` (within 11% if `desiredCapacity >= 1000`).
`protected static void`	`statistics(int from, int to)`	Tests correctness.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - largestPrime
```
public static final int largestPrime
```
    The largest prime this class can generate; currently equal to Integer.MAX_VALUE.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - PrimeFinder
```
protected PrimeFinder()
```
    Makes this class non instantiable, but still let's others inherit from it.
- Method Detail
  - main
```
protected static void main(String[] args)
```
    Tests correctness. Try from=1000, to=10000 from=200, to=1000 from=16, to=1000 from=1000, to=Integer.MAX_VALUE
  - nextPrime
```
public static int nextPrime(int desiredCapacity)
```
    Returns a prime number which is >= desiredCapacity and very close to desiredCapacity (within 11% if desiredCapacity >= 1000).
    
    Parameters:
    
    desiredCapacity - the capacity desired by the user.
    
    Returns:
    
    the capacity which should be used for a hashtable.
  - statistics
```
protected static void statistics(int from,
                                 int to)
```
    Tests correctness.